1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to achieving lower vertical stiffness values in a suspension while retaining in large part the torsion properties normally thought to be compromised by decreasing suspension stiffness. In a further aspect, the invention provides for the retention of intended gram load values of the suspension despite backbending of the suspension that may occur during head stack assembly, combing or other mechanical operations that cause the suspension to be bent, even briefly, along its longitudinal axis. In general, these results are realized by removing selected metal layer material from the suspension in the spring portion and in the adjacent distal portion and/or base portion as well. Sway resonant frequency is also improved with the invention.
2. Description of the Related Art
Each suspension application has a vertical stiffness requirement. Selection of suspension spring portion length, thickness width, within the overall size limitations imposed by the application determines the vertical stiffness, with increased width associated with increased stiffness. In general, vertical stiffness is desirably minimized. Torsional frequency response of a suspension, a function of torsion stiffness, herein generally called simply torsion, is desirably maximized and this can be done by increasing the width of the spring portion, within limits imposed by the application and the need to keep stiffness low. There is thus a trade-off between stiffness and torsion that is generally resolved by using a wide spring portion and having a hole in the center thereof to reduce the volume of metal and keep width or lateral extent up.